Q: Does the iPad 3G GPS work without a data plan?
A: The short answer is yes, although if you’re using the built-in Maps application you will still require a data connection—either cellular or Wi-Fi—in order to actually download the Google Maps data, since this is not stored locally on the device. If you have no Internet connection at all you will need to use a third-party application that stores map data locally on your device.
The iPhone and iPad 3G contain an actual GPS receiver but also use a technology known as Assisted GPS (AGPS) which references cellular towers to provide a faster GPS fix. Normally, a GPS received must be able to receive a signal from several GPS satellites in order to provide an accurate location fix, but of course this assumes that you’re potential location is anywhere on the surface of the earth. Identifying nearby cellular towers provides a very quick approximate location requiring less time and fewer satellite signals to determine your specific position. Note, however, that AGPS does not require a cellular data connection in order to find nearby towers, so you don’t specifically require a data plan to use it, although on an iPad 3G, no data plan likely means no cellular connection at all.
This would normally result in the iPad taking a longer time to find your location, however the Location Services in iOS also use nearby Wi-Fi access points in much the same way as cellular towers to assist the GPS lookup process, meaning that as long as you have Wi-Fi turned on and are in an area with one or more nearby Wi-Fi access points you should still get a reasonably quick location fix. Keep in mind as well that you don’t need to be connected to any Wi-Fi networks for this purpose—iOS Location Services looks at all of the access points that it can see nearby whether you’re connected to them or not.
At worst if you are travelling in a remote area with your iPad 3G and no cellular data connection or nearby Wi-Fi you will find that a GPS fix can take up to five minutes to happen, but you’ll still eventually get one. As noted earlier, however, you’ll still need to be using an app with locally-stored maps to see your location indicated on an actual map.